High Stiffness Shape Memory Alloy Actuated Aerostructure

ABSTRACT

A shape memory alloy (SMA) actuated aerostructure operable to dynamically change shape according to flight conditions is disclosed. Deformable structures are actuated by SMA actuators that are coupled to face sheets of the deformable structures. Actuating the SMA actuators produces complex shape changes of the deformable structures by activating shape changes of the SMA actuators. The SMA actuators are actuated via an active or passive temperature change based on operating conditions. The SMA actuated aerostructure can be used for morphable nozzles such as a variable area fan nozzle and/or a variable geometry chevron of a jet engine to reduce engine noise during takeoff without degrading fuel burn during cruise.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 12/537,002, entitled “High Stiffness Shape MemoryAlloy Actuated Aerostructure” filed on Aug. 6, 2009, the content ofwhich is incorporated herein by reference in its entirety.

FIELD

Embodiments of the present disclosure relate generally to shape memoryalloy structures. More particularly, embodiments of the presentdisclosure relate to shape memory alloy structures operable to affectfluid flow.

BACKGROUND

An airplane's airframe and engines may produce varying amounts ofaudible noise and turbulent drag during different flight conditions. Oneof the main sources of noise and drag is the air flow aroundaerostructure surfaces. Leading and trailing wing surfaces, controlsurfaces, landing gear structures, air flow around turbofan enginesurfaces, and turbofan engine exhaust flow may produce noise. As flightconditions change, the velocity, temperature, pressure, turbulence, andother properties of the air and exhaust can change considerably. Ontakeoff and landing, the external air (free stream air) velocity may belower, temperatures higher, and engine exhaust power at a maximum (i.e.,for takeoff). During cruise, the external air (free stream air) velocitymay be higher, temperatures lower, and turbofan engine exhaust power ata cruise level. From ground to cruising altitude, all of these factorsmay vary in complex non-linear ways for various flight conditions.

In order to improve aircraft performance across all phases of flightsuch as by reducing takeoff noise and reducing drag during cruise whileminimizing weight, an aircraft design should include optimized shapesand physical properties (such as stiffness) of the aerostructures.However, the optimal shape and other properties change depending on theflight conditions. Thus, it may be desirable for an aerostructure to bedynamically reconfigurable in order to change to adapt to the currentflight conditions.

Of particular interest is the noise and drag from the engines.Conventional turbofan engines include a fan section and an engine core,with the fan section having a larger outer diameter than that of theengine core. The fan section and the engine core are disposedsequentially about a longitudinal axis and are enclosed in a nacelle. Anannular path of primary airflow (core flow) passes through the fansection and the engine core (core nozzle) to generate primary thrust. Anannular path of fan flow, disposed radially outward of the core airflowpath, passes through the fan section and exits through a nozzle (fannozzle) to generate fan thrust.

The requirements for takeoff and landing conditions are different fromrequirements for a cruise condition. For cruise conditions, it isdesirable to have a smaller diameter fan nozzle for increasing cruiseperformance and for maximizing fuel efficiency, whereas, for takeoff andlanding conditions, smaller diameter fan nozzles may not be consideredoptimum. Therefore, in many conventional engines, cruise performance andfuel efficiency are often compromised to ensure safety of the turbofanengine at take-off and landing. In addition to improved efficiency,varying the fan nozzle area and hence the engine bypass ratio is anextremely effective means of reducing community noise during takeoff andapproach. Some turbofan engines have implemented variable area fannozzles (VAFN). VAFN have the ability to have a smaller fan nozzlediameter during cruise conditions and a larger fan nozzle diameterduring take-off and landing conditions.

With present day jet aircraft, structures typically known in theindustry as “chevrons” have been used to help in suppressing noisegenerated by a jet engine. Chevrons have traditionally been, triangular,tab-like elements located along a trailing edge of fan and core nozzlesof turbofan jet engines such that they project into the exhaust gas flowstream exiting from the fan and core nozzles. For a wide range ofoperating conditions, chevrons have proven to be effective in reducingbroadband noise generated by the mixing of airflows from the core nozzleand fan nozzle, and the mixing of airflows from the fan nozzle and freestream air. Since the chevrons can interact directly with the fan flow,however, they also generate drag and loss of thrust. Consequently, thereis a tradeoff between the need to attenuate noise, and minimizing theloss of thrust due to the presence of the chevrons.

Thus, there is a need for technology which provides the needed noiseattenuation but does not produce additional drag or loss of thrustduring cruise conditions.

SUMMARY

A shape memory alloy (SMA) actuated aerostructure operable todynamically change shape according to flight conditions is disclosed.Deformable structures are actuated by SMA actuators that are coupled toface sheets of the deformable structures. Actuating the SMA actuatorsproduces complex shape changes of the deformable structures byactivating shape changes of the SMA actuators. The SMA actuators areactuated via an active or passive temperature change based on operatingconditions. The SMA actuated aerostructure can be used for morphablenozzles such as a variable area fan nozzle and/or a variable geometrychevron of a jet engine to reduce engine noise during takeoff withoutdegrading fuel burn during cruise.

A first embodiment comprises a shape memory alloy actuatedaerostructure. The shape memory alloy actuated aerostructure comprises afirst face sheet and a second face sheet. The shape memory alloyactuated aerostructure further comprises at least one shape memory alloyactuator coupled to the first face sheet at at least one location on thefirst face sheet and coupled to the second face sheet at a plurality oflocations on the second face sheet.

A second embodiment comprises a system for shaping a shape memory alloyactuated aerostructure in response to temperature changes. The systemcomprises at least one shape memory alloy actuated aerostructure whichcomprises a first face sheet, a second face sheet, and at least oneshape memory alloy actuator located between the first face sheet and thesecond face sheet. The shape memory alloy actuator is coupled to thefirst face sheet at at least one location on the first face sheet andcoupled to the second face sheet at a plurality of locations on thesecond face sheet. The system further comprises a controller operable toactivate at least one region of the at least one shape memory alloyactuator to morph the at least one shape memory alloy actuatedaerostructure.

A third embodiment comprises a method for operating a shape memory alloyactuated aerostructure. The method comprises determining at least onecharacteristic of the shape memory alloy actuated aerostructure to beoptimized, and controlling a temperature of at least one portion of atleast one shape memory alloy actuator to optimize the at least onecharacteristic. The shape memory alloy actuator is located between afirst face sheet and a second face sheet of the shape memory alloyactuated aerostructure, and is coupled to the first face sheet at atleast one location on the first face sheet and coupled to the secondface sheet at two or more locations on the second face sheet.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF DRAWINGS

A more complete understanding of embodiments of the present disclosuremay be derived by referring to the detailed description and claims whenconsidered in conjunction with the following figures, wherein likereference numbers refer to similar elements throughout the figures. Thefigures are provided to facilitate understanding of the disclosurewithout limiting the breadth, scope, scale, or applicability of thedisclosure. The drawings are not necessarily made to scale.

FIG. 1 illustrates a simplified side view of an aircraft turbofan enginenacelle showing a morphable fan nozzle comprising a plurality ofdeformable structures according to an embodiment of the disclosure.

FIG. 2 illustrates a simplified schematic cross sectional view of theturbofan engine nacelle of FIG. 1 showing two of the deformablestructures of the morphable fan nozzle according to an embodiment of thedisclosure.

FIG. 3 illustrates various schematic profiles that each of thedeformable structures of FIG. 1 can be morphed into according to variousembodiments of the disclosure.

FIG. 4 illustrates a schematic view of a portion of the morphable fannozzle of FIG. 1 showing an exemplary shape memory alloy (SMA) actuatedaerostructure as an example of a deformable structure according to anembodiment of the disclosure.

FIG. 5 illustrates a morphing system showing an enlarged schematic viewof the exemplary SMA actuated aerostructure shown in FIG. 4 according toan embodiment of the disclosure.

FIG. 6 illustrates schematic perspective views of an exemplary SMAactuated aerostructure prior-to-assembly and after-assembly according toan embodiment of the disclosure.

FIG. 7 illustrates a schematic perspective view of an exemplaryassembled SMA actuated aerostructure at a first actuated state, a secondactuated state, and an overlay of the first and second actuated states.

FIG. 8 illustrates a side view of an exemplary assembled SMA actuatedaerostructure according to an embodiment of the disclosure.

FIG. 9 illustrates a side view of the exemplary assembled SMA actuatedaerostructure of FIG. 8 in an actuated state.

FIG. 10 illustrates perspective views of an exemplary SMA actuatedaerostructure that can be used to form a VAFN panel according to anembodiment of the disclosure.

FIG. 11 illustrates perspective top views of exemplary SMA actuatedaerostructures utilizing “strips”, “lattice”, “connected strips”, and“I-beam” SMA actuators respectively according to various embodiments ofthe disclosure.

FIG. 12 illustrates schematic views of two morphable fan nozzles showingtwo exemplary SMA actuated aerostructures incorporating the “Strips” SMAactuator and the “Lattice” SMA actuator of FIG. 11 respectivelyaccording to two embodiments of the disclosure.

FIG. 13 is a flow chart showing an exemplary process for operating anSMA actuated aerostructure according to an embodiment of the disclosure.

FIG. 14 illustrates an SMA actuated aerostructure showing 3-dimensionalshape changes of a VAFN panel in response to temperature changes at oneor more segments of one or more SMA actuators according to an embodimentof the disclosure.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the disclosure nor theapplication and uses of such embodiments. Furthermore, there is nointention to be bound by any expressed or implied theory presented inthe preceding technical field, background, brief summary or thefollowing detailed description.

Embodiments of the disclosure are described herein in the context ofpractical non-limiting applications, namely, morphable fan nozzlescomprising variable fan nozzle panels and/or variable geometry chevrons.Embodiments of the disclosure, however, are not limited to such morphingfan nozzles applications, and the techniques described herein may alsobe utilized in other morphing applications. For example, embodiments maybe applicable to fluid dynamic surfaces, other aircraft structures,automotive structures, robotics, other morphable structures comprisingsuitable geometries to alter a fluid flow, and the like.

Embodiments of the disclosure may be described herein in terms offunctional and/or logical block components and various processing steps.It should be appreciated that such block components may be realized byany number of hardware, software, and/or firmware components configuredto perform the specified functions. For the sake of brevity,conventional techniques and components related to signal processing,aircraft control systems, high lift devices, and other functionalaspects of the systems (and the individual operating components of thesystems) may not be described in detail herein. In addition, thoseskilled in the art will appreciate that embodiments of the presentdisclosure may be practiced in conjunction with a variety of differentaircraft control systems and aircraft wing configurations and engines,and that the system described herein is merely one example embodiment ofthe disclosure.

FIG. 1 illustrates a simplified side view of an aircraft turbofan enginenacelle 100 (nacelle 100) showing a morphable fan nozzle comprising aplurality of deformable structures according to an embodiment of thedisclosure. The nacelle 100 is a housing separate from the fuselage (notshown) that holds a jet engine (not shown) for an aircraft. The nacelle100 may comprise an engine inlet (not shown), a fan cowl 102, thrustreverser (not shown), a core flow nozzle 104, a morphable fan nozzle106, and a control mechanism 122.

The core flow nozzle 104 provides a controlled vent for hot turbineengine exhaust. A turbofan engine provides thrust (i.e., a gas flow)from both the core flow 118 (gas flow) of the hot turbine engine exhaustfrom the core flow nozzle 104, and the fan flow 116 (gas flow) from theturbofan powered by the turbine engine. In order to reduce noise, thecore flow nozzle 104 may have chevrons (not shown). The core flow 118generally has a higher velocity than the fan flow 116.

The morphable fan nozzle 106 may comprise a plurality of deformablestructures 108 configured to alter a flow. In the embodiment shown inFIG. 1, each of the deformable structures 108 comprises a VAFN panel 110coupled to a variable geometry chevron (VGC) 112. The deformablestructures 108 may extend from a lip area 114 of the morphable fannozzle 106. The deformable structures 108 may be arrangedcircumferentially around the entire lip area 114 of the morphable fannozzle 106. However, the deformable structures 108 may be located at anylocation, suitable to alter a flow. Each of the deformable structures108 of the morphable fan nozzle 106 is not limited to the VAFN panel 110and/or the VGC 112 of this embodiment and other structures may also beused. The deformable structures 108 may comprise structures that are,without limitation, triangular, chambered, rectangular, circular, or acombination thereof, and the like.

As will be described in greater detail below, according to variousembodiments of the disclosure, each of the deformable structures 108comprises one or more shape memory alloy (SMA) actuators operable todeform (i.e., bend, deflect, change shape) each of the deformablestructures 108 in response to heating and/or cooling. In this manner,each of the deformable structures 108 can change shape in one or moredimensions to alter the flow. For example, each of the deformablestructures 108 can change shape to reduce the noise produced byoperation of the turbofan engine of an aircraft as explained in moredetail below in the context of discussion of FIGS. 2-3.

The control mechanism 122 is configured to thermally control extensionof each of the deformable structures 108 into the flow path of the fanflow 116 for a first set of flight conditions (e.g., take off, landingand approach) to reduce the airflow noise. The control mechanism 122also thermally controls extension of each of the deformable structures108 away from the flow path of the exhaust flow for a second set offlight conditions (e.g., cruise) to maximize fuel efficiency. In oneembodiment, the control mechanism may comprise a passive controlmechanism to control the deformation of each of the deformablestructures 108 based on an ambient temperature corresponding to analtitude at a flight condition. In another embodiment, the controlmechanism 122 may include or be realized as a controller (connected tothe aircraft systems), as explained below in the context of FIG. 5 tofacilitate controlling the deformation (i.e., changing the shape) ofeach of the deformable structures 108.

FIG. 2 illustrates a simplified schematic cross sectional view of theturbofan engine nacelle showing two of the deformable structures 202 ofthe morphable fan nozzle 200 according to an embodiment of thedisclosure. The embodiment shown in FIG. 2 comprises a fan cowl 204 (102in FIG. 1) which includes a plurality of deformable structures 202 (108in FIG. 1), and a turbofan engine 206. The deformable structures 202 maycomprise a VAFN panel 110 extending from the trailing edge lip area 208of the morphable fan nozzle 200 and coupled to a VGC 112 at a VGCattachment location 210. In one embodiment, the VGC 112 may be deployedby an amount d1 into the fan flow 116 when actuated by an SMA actuatoras explained in more detail below. d1 may be, for example but withoutlimitation, about 1.5 inches. Additionally, the VAFN panel 110 mayextend by an amount d2 when actuated by the SMA actuator as explained ingreater detail below. In one embodiment, d2 may be, for example butwithout limitation, about 1.5 inches, which results in an about 20percent increase in area of the morphable fan nozzle 200 (morphable fannozzle 106 in FIG. 1). In this manner, the deformable structures 202(108 in FIG. 1) changes a shape of the morphable fan nozzle 106/200 froma non-actuated profile or a nominal profile to an actuated profile thatcan suitably alter characteristics of the fan flow 116 based on variousflight conditions as explained in more detail below.

FIG. 3 illustrates schematic profiles that each of the deformablestructures (i.e., VAFN panel plus VGC, VCG only, VAFN panel only) of themorphable fan nozzle 106/200 of the FIG. 1 and FIG. 2 can be morphedinto according to various embodiments of the disclosure. FIG. 3 shows anominal profile 310, and a plurality of actuated profiles 320, 330, and340 of the deformable structures 202/108. The nominal profile 310 showsa nominal VAFN panel profile 312 for a non-actuated VAFN panel 110 thatmay be coupled to a VGC 112 at an attachment point 318, and a nominalVGC profile 314 for a non-actuated VGC 112. The nominal (non-actuated)profiles 312 and 314 are compared to their respective actuated profiles320, 330, and 340 below.

The actuated profile 320 shows an exemplary actuated state of thedeformable structures 202 comprising the VAFN panel 110 coupled to theVGC 112 (FIG. 2) at the attachment point 326 (VGC attachment location210 in FIG. 2). The actuated profile 320 comprises an actuated VAFNpanel profile 322, and an actuated VGC profile 324. As shown by theactuated VAFN panel profile 322, if the VAFN panel 110 is actuated by anSMA actuator, the VAFN panel 110 is deflected/deployed outward into thefree stream flow 120 (FIG. 2) and away from the fan flow 116 by anamount d2 as compared to the nominal VAFN panel profile 312. Also, asshown by the actuated VGC profile 324, if the VGC 112 is actuated by anSMA actuator, the VGC 112 deploys into the fan flow 116 by an amount d1compared the nominal VGC profile 314. In this manner, according to thisembodiment (deformable structures each comprising a VAFN panel and aVGC) the deformable structures 202 reduce the noise caused by theturbofan engine (FIG. 1) via two different mechanisms. In the firstmechanism, the VAFN panel 110 is deflected/deployed outward into thefree stream flow 120 (pulled back out of the fan flow 116) to increasearea (i.e., by about 10%) of the morphable fan nozzle 106 based on theamount d2. The increase in the area of the morphable fan nozzle 106causes a decrease in velocity of the fan flow 116 that is moving throughthe morphable fan nozzle 106, thereby making the engine quieter. Thesecond mechanism involves introducing vortices (turbulence) into the fanflow 116 by deploying the VCG 112 (i.e., triangular chevron) into thefan flow 116. In this manner, the VGC 112 may deform such that itextends (i.e., “deploys”) partially by an amount d1 into a path of thefan flow 116 exiting from the morphable fan nozzle 106 to promote mixingof the fan flow 116 in proximity or adjacent to free stream flow 120 andthereby reducing noise. During cruise and other flight conditions, eachof the deformable structures 108/202 may return to the nominal profile310, or other shapes.

The actuated profile 330 shows an exemplary actuated state of each ofthe deformable structures 202 comprising the VAFN panel 110 (i.e.,without the VGC 112). The actuated profile 330 comprises an actuatedVAFN panel profile 322. As shown by the actuated VAFN panel profile 332,if the VAFN panel 110 is actuated by an SMA actuator, the VAFN panel 110is deflected/deployed outward into the free stream flow 120 (FIG. 2) andaway from the fan flow 116 by an amount d2 as compared to the nominalVAFN panel profile 312. In this manner, according to this embodiment(i.e., a morphable fan nozzle with VAFN panel 110 and without the VGC112), the deformable structures 202 can reduce the noise caused by theturbofan engine (FIG. 1) via the first mechanism as explained above.

The actuated profile 340 shows an exemplary actuated state of each ofthe deformable structures 202 comprising a constant area fan nozzlepanel (CAFN panel) coupled to the VGC 112 at the attachment point 344.The actuated profile 340 comprises a nominal VAFN panel profile 312, andan actuated VGC profile 342. Since the CAFN panel is not actuated, itmay not contribute to changing the shape of the deformable structures202; therefore, the nominal VAFN panel profile 312 also represents theCAFN panel profile in the actuated profile 340. As shown by the actuatedVGC profile 342, if the VGC 112 is actuated by an SMA actuator, the VGC112 deploys into the fan flow 116 by an amount d1 compared the nominalVGC profile 314. In this manner, according to this embodiment(deformable structures each comprising a CAFN panel and a VGC) thedeformable structures 202 reduce the noise caused by the turbofan engine(FIG. 1) via the second mechanism as explained above.

FIG. 4 illustrates a schematic view 400 of a portion 124 of themorphable fan nozzle 106 of FIG. 1 showing an exemplary SMA actuatedaerostructure 408 as an exemplary deformable structure according to anembodiment of the disclosure. The SMA actuated aerostructure 408 maycomprise one or more substantially sinusoidal, or the like, SMAactuators 406.

A shape memory alloy (SMA) remembers its original shape after beingdeformed from that original shape. An SMA returns to its original shapewhen it is heated (shape memory effect) or when the deforming pressureis removed (superelasticity). An SMA that returns to its original shapewhen heated is a one-way SMA. A two-way SMA remembers two differentshapes: one shape at a relative low temperature, and another shape at arelative high temperature. Setting the two shapes by thermo-mechanicalprocessing is known as “training” the SMA. An SMA with the two shapesset is known as a “trained” SMA. The shape properties of a trained SMAresult from a temperature initiated martensitic phase transformationfrom a low symmetry (martensite) to a highly symmetric (austenite)crystal structure. The temperatures at which the SMA changes itsstructure depend on the particular alloy, and can be tuned by varyingthe chemical mix and thermo-mechanical processing. Some common SMAmaterials are copper-zinc-aluminum, copper-aluminum-nickel,nickel-titanium-platinum, nickel-titanium-palladium,nickel-titanium-hafnium and nickel-titanium (NiTi or Nitinol). NiTi SMAalloys generally have superior mechanical properties to copper-basedSMAs, but are also generally more expensive. The SMA actuators accordingto various embodiments of the disclosure may be made, for example butwithout limitation, from any of these aforementioned SMA materials.

Existing movable chevrons may use a single SMA that is a solid, flat ortapered bar actuator made of SMA material that is connected to only oneof the two face sheets that compose each of the chevrons. The existingdesigns do not take advantage of both face sheets. In this manner,existing designs do not allow three dimensional shape changes. Moreover,the existing designs use stiff structures to withstand the aero load.Therefore, large actuators are used to bend the structure, whichincreases the weight. Extra weight adversely affects the overallperformance of an aircraft. The additional weight reduces aircraft rangeand can result in additional fuel consumption for operation of theengine. Therefore, in turbofan engine fabrication, weight increasesshould be avoided since the weight increase resulting from the additionof a variable area fan nozzle can negate benefits gained from improvedfuel efficiency resulting from the reduced diameter of the variable areanozzle during cruise conditions.

As shown in FIG. 4 the sinusoidal SMA actuators 406 are located (i.e.,sandwiched) between a first face sheet 402 and a second face sheet 404of SMA actuated aerostructure 408 (deformable structure) according to anembodiment of the disclosure. In this manner, embodiments of thedisclosure provide for a stiff aerostructure that also changes shape. Asexplained above, the SMA actuators 406 can be made from SMA material toallow the SMA actuated aerostructure 408/108 to morph in multipledimensions such as three dimensions to form complex shape changes asexplained in more detail below.

FIG. 5 illustrates a morphing system 500 which shows an enlarged view ofthe SMA actuated aerostructure 408 shown in FIG. 4 according to anembodiment of the disclosure. The morphing system 500 may comprise anSMA actuated aerostructure 502 and a controller 504.

The SMA actuated aerostructure 502 may comprise an upper face sheet 506,a lower face sheet 508, and one or more SMA actuators 510 locatedtherebetween. The SMA actuated aerostructure 502 may be coupled to,without limitation, the lip area 114 of the turbofan engine nacelle 100,the trailing edge of a thrust reverser sleeve (not shown), the core flownozzle 104, or the like. In this embodiment the SMA actuatedaerostructure 502 may comprise a VAFN panel 512 (110 in FIG. 1) and aVGC 514 (112 in FIG. 1) as explained above in the context of discussionof FIGS. 1-3. The VAFN panel 512 may be coupled to the VGC 514 via a VGCattachment 516. The SMA actuated aerostructure 502 may also be used onother aircraft structures, automotive structures, fluid flow systems,and the like.

In one embodiment, the upper face sheet 506 may be located in contactwith or in proximity to a cold free stream flow 518 (free stream flow120 in FIGS. 1-2) when, for example, used in an aircraft morphable fannozzle application. Because the upper face sheet 506 needs to bedeformable, materials used for the upper face sheet 506 may require anappropriate amount of flexibility. Also, since in this embodiment theupper face sheet 506 is in a relatively lower temperature environment,the upper face sheet 506 may require less temperature resistance thanthe lower face sheet 508. The upper face sheet 506 may comprise, withoutlimitation, materials such as aluminum alloys, graphite composites,ceramic-metal composites, plastics, and the like.

The lower face sheet 508 may be located in contact with or in proximityto the hot fan flow 520 (fan flow 116 in FIGS. 1-2) when, for example,used in an aircraft morphable fan nozzle application. Because the lowerface sheet 508 needs to be deformable, materials used for the lower facesheet 508 may require an appropriate amount of flexibility. Also, sincein this embodiment the lower face sheet 508 is in a relatively highertemperature environment, the lower face sheet 508 may require a moretemperature resistance material than the upper face sheet 506. The lowerface sheet 508 may comprise materials such as, for example but withoutlimitation, higher temperature resistant aluminum alloys, graphitecomposites, ceramic-metal composites, higher temperature resistantplastics, and the like.

The SMA actuators 510 may be coupled to, for example but withoutlimitation, an inner surface (not shown) of the upper face sheet 506 andan inner surface 522 of the lower face sheet 508 at various connectionpoints such as connection points 524 and 526 respectively. For example,the SMA actuators 510 may be connected to the inner surface (not shown)of the upper face sheet 506 at at least one of the connection points 524and the inner surface 522 of the lower face sheet 508 at variousconnection points such as connection points 526 and vice versa. Theconnection points 524/526 may be located, for example but withoutlimitation, at substantially maxima and minima of the SMA actuators 510respectively. The SMA actuators 510 may be connected to the first andthe second face sheets 506/508 of the SMA actuated aerostructure 502,for example but without limitation, by rivets, adhesives, fastening,welding, brazing, bonding, and the like. Because the SMA actuators 510are connected to both face sheets 506/508 in multiple locations such as524/526, structure of the SMA actuated aerostructure 502 remains stiffin various configurations. In this manner, the load applied by the SMAactuators 510 to the rest of the SMA actuated aerostructure 502 isdistributed throughout the SMA actuated aerostructure 502. This allowsfor complex shape changes of the SMA actuated aerostructure 502.

In various embodiments, complex multi-dimensional shape changes such asthree-dimensional shape changes of the SMA actuated aerostructure 502are provided by activating shape changes of the SMA material. The SMAactuated aerostructure 502 may comprise multiple SMA actuators 510,which may be activated individually or in combinations and each invarying amounts of deformation. Furthermore, each of the SMA actuators510 may have heating or cooling elements at various locations. Forexample, the SMA actuators 510 may be heated in multiple sections of oneSMA strip, and/or multiple strips of the VGC 514 and/or VAFN panel 512may each be individually heated and controlled. Thus, each of the SMAactuators 510 may be deformed to varying degrees at one or more pointsin a controlled manner, and thus the one or more SMA actuators 510 maybe used in combination to form complex 3-dimensional shapes as explainedin more detail below in the context of FIG. 14.

A controller 504, may be located remotely from the SMA actuatedaerostructure 502, or may be coupled to the SMA actuated aerostructure502. The SMA actuators 510 are controllable by adjusting a temperaturebetween the martensite and austenite finish temperatures such thatshapes in between the extreme actuated states can be selected andmaintained using the controller 504. The controller 504 may beimplemented as part of the aircraft system, a centralized aircraftprocessor, a subsystem computing module devoted to the deferrablestructure arrangements explained above, or the like. In operation, thecontroller 504 may control the SMA actuated aerostructure 502 bymonitoring the temperature of the SMA actuators 510 and by heatingand/or cooling at least a portion of at least one of the SMA actuatorsas needed. The heating/cooling of the SMA actuators 510 may be providedby, for example but without limitation, the aircraft cooling/heatingsystems and the like. For example, a heater may utilize an electricalheater element and a controllable current source where the temperatureis proportional to the current applied to the heater element. In thismanner, the controller 504 determines a temperature based on a currentflight condition, and provides heating/cooling to activate/deactivatethe SMA actuators 510 as explained above. This enables the controller504 to control the actuation of the SMA actuated aerostructure 502 inaccordance with the current flight conditions, e.g., whether theaircraft is approaching, landing, taking off or in cruise. Thecontroller 504 may be used to optimize characteristics of the SMAactuated aerostructure 502 for noise, lift, drag, and the like.

FIG. 6 illustrates schematic perspective views of an exemplaryprior-to-assembly SMA actuated aerostructure 610 and an exemplaryafter-assembly (assembled) SMA actuated aerostructure 620. Theprior-to-assembly SMA actuated aerostructure 610 comprises a top facesheet 612, a bottom face sheet 614, and a complex SMA actuator 616. Asshown in FIG. 6, the prior-to-assembly SMA actuated aerostructure 610 isassembled into the assembled SMA actuated aerostructure 620 comprising acomplex shape. The assembled SMA actuated aerostructure 620 comprises atop face sheet 622, a bottom face sheet 624 and an SMA actuator 626according to an embodiment of the disclosure.

FIG. 7 shows an exemplary SMA actuated aerostructure 700 at a firstactuated state (first position) 712 (e.g., hot), at a second actuatedstate (second position) 714 (e.g., cold), and an overlay of the firstactuated state 712 and the second actuated state 714 showing a deployedposition d1 as explained above.

Prior to assembly (i.e., prior-to-assembly SMA actuated aerostructure610), the top face sheet 612, the bottom face sheet 614, and the SMAactuator 616 may each have their own respective shape, and afterassembly tension from their respective shapes can balance to form a highstiffness structure such as the assembled SMA actuated aerostructure620.

Embodiments of the disclosure can be used in either a one-way or atwo-way shape memory effect. In a case of one-way shape memory effect,the assembled SMA actuated aerostructure 620 itself provides the forcethat deforms the SMA material when cooling. Upon heating, the shapememory effect can bring the assembled SMA actuated aerostructure 620back to its starting point.

A pre-forming of the face sheets 612/614 may be used with a one-way SMAactuator to give the prior-to-assembly SMA actuated aerostructure 610 afirst position 714 (cold position 714) when cold and a second position712 (hot position 712) when hot. When an SMA actuator is in its coldstate, the SMA material (i.e., metal) can be bent or stretched into avariety of new shapes and can hold that shape until it is heated abovethe transition temperature. Upon heating, the shape changes back to itsoriginal shape, regardless of the shape it was morphed to when cold.When the metal cools again it can remain in the original shape, untildeformed again (e.g., by tension of the face sheets 622/624). Thus, theSMA actuator 616 is given an original shape prior-to-assembly, and theassembled SMA actuated aerostructure 620 has a cold position 714. Whenthe SMA actuator 626 is heated, the assembled SMA actuated aerostructure620 is repositioned by the SMA actuator 626 to hot position 712, andwhen the SMA actuator 626 is cooled, the tension of the face sheets622/624 return the assembled SMA actuated aerostructure 620 to coldposition 714.

For a two-way SMA actuator, the SMA remembers two different shapes: oneat low temperatures, and one at high temperatures. The two differentshapes can be obtained without the application of an external force fromthe face sheets 622/624. The assembled SMA actuated aerostructure 620has a cold position 714 with the SMA actuator 626. When the SMA actuator626 is heated, the assembled SMA actuated aerostructure 620 isrepositioned by the SMA actuator 626 to hot position 712, and when theSMA actuator 626 is cooled, the SMA actuator 626 returns the SMAactuated aerostructure 620 to the cold position 714.

As explained above, the temperature change may be allowed to occurpassively from, for example but without limitation, the heating from theengine, ambient air or be made actively by heating and cooling devicesattached to the SMA actuator 626 and controlled by the controller 504.Different parts of the SMA actuator 626 may be heated or cooledseparately. For example, each section of the SMA actuator 626 locatedbetween its connection points (e.g., 524/526 in FIG. 5) may be heatedseparately. Controlling a temperature at each section of the actuatorallows control of a shape of each section, and control of an angle and adegree of curvature of the SMA actuator 626 as explained in more detailbelow in the context of FIG. 14.

FIG. 8 illustrates a side view of an exemplary assembled SMA actuatedaerostructure 800 at a nominal state (non-actuated state) incorporatingfasteners to attach the SMA actuators 810 to its face sheets. Asexplained above, various methods may be used to attach the shape memoryalloy actuators 810 to face sheets of the SMA actuated aerostructure800, for example but without limitation, braising, welding, glue,fasteners, rivets, and the like.

FIG. 9 illustrates a side view of an exemplary assembled SMA actuatedaerostructure 900 at an actuated state (shown in FIG. 8 at anon-actuated state). The assembled SMA actuated aerostructure 900 can beused to provide a high stiffness deformable structure for variousapplications such as changing the area of the morphable fan nozzle 106at various flight conditions.

FIG. 10 illustrates perspective views of an exemplary SMA actuatedaerostructure at a first actuated state 1010 and a second actuated state1020. The SMA actuated aerostructures can be used to form the VAFN panel110 as explained above. The SMA actuated aerostructure at the firstactuate state 1010 comprises a first face sheet 1012, a second facesheet 1014, and one or more actuators 1016 therebetween. The SMAactuated aerostructures at the second actuated state 1020 comprises afirst face sheet 1022, a second face sheet 1024, and one or moreactuators 1026 therebetween. The SMA actuated aerostructures can beactuated via the SMA actuators 1016/1026 to change its shape form itsfirst actuated state 1010 to its second actuated state 1020 in responseto a temperature change as explained below in the context of discussionof FIGS. 13-14.

FIG. 11 illustrate perspective top views of exemplary SMA actuatedaerostructures 1110, 1120, 1130, and 1140 utilizing “strips” 1112,“lattice” 1122, “connected strips” 1132, and “I-beam” 1142 SMA actuatorsrespectively according to various embodiments of the disclosure.

The particular topological features of the examples shown in FIG. 11 areamong a number of possible embodiments of the disclosure and othertopological features may also be used. Each of the SMA actuators 1112,1122, 1132, and 1142 can be used, for example, in the morphable fannozzle 106/200 for providing a high stiffness when secured between thetwo face sheets (506/508 FIG. 5) of each of the deformable structures108 on the trailing edge lip area 114/208 of the morphable fan nozzle106. For example, FIG. 12 illustrate schematic views of two morphablefan nozzles 1210 and 1220 showing exemplary SMA actuated aerostructuresincorporating the “Strips” 1112 SMA actuator and the “Lattice” 1122 SMAactuator of FIG. 11 respectively.

Various shapes can be used for the SMA actuators 1112, 1122, 1132, and1142 to optimize a design for weight, temperature resistance, stiffness,and the like.

Noise reduction is most needed for takeoff of an aircraft and to alesser degree during cruise. Thus, any noise reduction system/devicethat reduces noise at takeoff (i.e., a high thrust condition) ideallyshould not significantly degrade the fuel burn during cruise. Acompromise therefore exists between the design of the SMA actuatedaerostructures (deformable structures) for noise abatement and the needfor low cost operation during cruise and other flight segments.

FIG. 13 illustrates an exemplary flow chart showing a process 1300 foroperating an SMA actuated aerostructure according to an embodiment ofthe disclosure. Process 1300, provides for controlling temperature ofSMA actuator to optimize characteristic of the SMA actuatedaerostructure. The various tasks performed in connection with process1300 may be performed by software, hardware, firmware, or anycombination thereof. For illustrative purposes, the followingdescription of process 1300 may refer to elements mentioned above inconnection with FIGS. 1-12. In practical embodiments, portions ofprocess 1300 may be performed by different elements of the morphingsystem 500 for reducing airflow noise, e.g., the SMA actuatedaerostructures, the SMA actuators, and the controller. Process 1300 isdescribed in terms of one of the example embodiments described herein,namely, SMA actuators to morph (e.g., deploy, change shape, retract) theSMA actuated aerostructures.

Process 1300 for operating a SMA actuated aerostructure may begin bymonitoring a temperature (task 1302). Process 1300 modifies thetemperature actively by a controller connected to the aircraft systemsas described in the context of FIG. 5 above, or alternatively may usethe ambient temperature, the engine temperature and the like topassively change the temperature of the SMA actuators at various flightconditions. In practice, the SMA actuators remember their original shapeafter being deformed from that original shape. In this manner, the SMAactuators return to an original shape when heated or when a deformingpressure is removed. As mentioned above, a two-way SMA remembers twodifferent shapes: one shape at a relative low temperature, and anothershape at a relative high temperature. Setting the two shapes can beaccomplished by thermal-mechanically “training” the SMA. In this manner,for example, the SMA actuators can be trained to remember variouspositions corresponding to various shapes of the deformable structuresuitable for reducing noise and associated drag for a range of flightconditions such as cruise and landing. These properties result fromtemperature initiated martensitic phase transformation from a lowsymmetry (martensite) to a highly symmetric (austenite) crystalstructure.

As mentioned above, in various embodiments, the SMA actuators are,without limitation, formed from a material in the family oftitanium-nickel alloys that have shape memory and superelasticproperties. In this manner, if the flight condition corresponds to thecruise temperature range (inquiry task 1304), then the temperature ofthe trained SMA actuators are changed to that of the cruise condition(task 1306). For example, the trained SMA actuators may be thermallydeactivated to return to a martensite shape. Then the deformablestructure suitably deforms (task 1309) for the cruise flight conditions.For a cruise condition, for example, the temperature may be about −40°C. In this manner, each of the SMA actuated aerostructures (i.e., eachof the deformable structures such as a VAFN panel) can deform from afirst position away from the flow path of the fan flow to a secondposition adjacent (or in proximity) to the flow path to minimize thrustspecific fuel consumption (TSFC) to improved fuel efficiency. Forexample, without limitation, thermally deactivating the SMA actuator toreturn to its martensite shape allows the area of the morphable fannozzle to decrease for the cruise flight conditions.

Otherwise, process 1300 changes the temperature of the trained SMAactuators to the temperature corresponding to the takeoff, flightconditions (task 1308), and thermally activates the SMA actuators. Inthis manner, each of the SMA actuated aerostructures such as the VAFNpanel is deformed (deflected/deployed) from a first position adjacent(or in proximity) to the flow path to a second position extendingoutward into the free stream flow (pulled back out of the fan flow). Asexplained above, the increase in the area of the morphable fan nozzlecauses a decrease in velocity of fan flow that is moving through themorphable fan nozzle, thereby making the engine quieter.

In one embodiment, the controller is configured to change temperature ofthe SMA actuators non-uniformly. The controller may vary temperatures ofrespective segments of each of the at least one SMA actuators separatelyfrom each other, wherein each of the temperatures are different from oneanother. In this manner, different regions of a 3-dimensional SMAactuator can be heated to different temperatures via the controller toeffect different levels of deformation in different regions of thestructure. For example as mentioned above, different actuators can beheated by different amounts to maintain a desired shape.

In various embodiments, complex 3-dimensional shape changes of the SMAactuated aerostructure are provided by activating shape changes of theSMA material. There may be multiple SMA actuators in the SMA actuatedaerostructure, which may be activated individually or in combinationsand each in varying amounts of deformation. Furthermore, each of the SMAactuators may have heating or cooling elements at various locations. Forexample, the SMA actuators may be heated in multiple sections of one SMAstrip, and/or multiple strips per SMA actuated aerostructure may each beindividually heated and controlled. Thus, each of the SMA actuators maybe deformed to varying degrees at one or more points in a controlledmanner, and thus the one or more SMA actuators may be used incombination to form complex 3-dimensional shapes.

FIG. 14 illustrates an SMA actuated aerostructure 1400 showing3-dimensional (3-D) shape changes of the VAFN panel in response totemperatures changes at various segments of one or more SMA actuatorsaccording to an embodiment of the disclosure. The embodiment shown inFIG. 14 may share similar features and functionalities to the morphingsystem 500. Common features, functions, and elements will not beredundantly described here. The SMA actuated aerostructure 1400comprises a top face sheet 1402, a bottom face sheet 1404, and SMAactuators 1406 located therebetween. The SMA actuators 1406 can beheated at various sections S1-S3 to various temperatures T1-T3respectively to morph to various actuated states (1010 and 1020 in FIG.10). In this manner, the SMA actuators 1406 can morph the SMA actuatedaerostructure 1400 into various shapes comprising various angles anddegree of curvature to obtain suitable profiles to alter the fan flow116 as described above in the context of discussion of FIG. 3. Absolutetemperatures required to effect actuation of the SMA actuators dependson the particular heat treatment used to produce the SMA actuators andmay be selected based on an intended application. For example butwithout limitation, the temperatures T1-T3 may be about 20° C. to 80°C., or given a different heat treatment T1-T3 might be 50° C. to 120° C.

Morphable aerostructures can result in reduced weight and more accurateshape changes of an aerosurface because of the improvement over theexisting solutions. Morphing aerosurfaces have the potential to reducedrag, increase lift, reduce noise, and improve fuel efficiency. A lightweight morphing structure which can undergo complex shape changespermits a morphable fan nozzle of a turbofan engine to change area atvarious flight conditions, but can also be stiff enough to resistloading such as pressure from air flow through the fan nozzle.

With the high stiffness shape memory alloy actuated aerostructureaccording to various embodiments of the disclosure, area of a fan nozzleof a turbofan engine can vary to reduce the noise from the turbofanengine during a takeoff while fuel burn during cruise is not degraded.

While at least one example embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexample embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the subject matterin any way. Rather, the foregoing detailed description will providethose skilled in the art with a convenient road map for implementing thedescribed embodiment or embodiments. It should be understood thatvarious changes can be made in the function and arrangement of elementswithout departing from the scope defined by the claims, which includesknown equivalents and foreseeable equivalents at the time of filing thispatent application.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as mean “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; and adjectivessuch as “conventional”, “traditional”, “normal”, “standard”, “known”,and terms of similar meaning should not be construed as limiting theitem described to a given time period or to an item available as of agiven time, but instead should be read to encompass conventional,traditional, normal, or standard technologies that may be available orknown now or at any time in the future. Likewise, a group of itemslinked with the conjunction “and” should not be read as requiring thateach and every one of those items be present in the grouping, but rathershould be read as “and/or” unless expressly stated otherwise. Similarly,a group of items linked with the conjunction “or” should not be read asrequiring mutual exclusivity among that group, but rather should also beread as “and/or” unless expressly stated otherwise. Furthermore,although items, elements or components of the disclosure may bedescribed or claimed in the singular, the plural is contemplated to bewithin the scope thereof unless limitation to the singular is explicitlystated. The presence of broadening words and phrases such as “one ormore”, “at least”, “but not limited to”, or other like phrases in someinstances shall not be read to mean that the narrower case is intendedor required in instances where such broadening phrases may be absent.

The above description refers to elements or nodes or features being“connected” or “coupled” together. As used herein, unless expresslystated otherwise, “connected” means that one element/node/feature isdirectly joined to (or directly communicates with) anotherelement/node/feature, and not necessarily mechanically. Likewise, unlessexpressly stated otherwise, “coupled” means that oneelement/node/feature is directly or indirectly joined to (or directly orindirectly communicates with) another element/node/feature, and notnecessarily mechanically. Thus, although FIGS. 1, 2, 4-12, and 14 depictexample arrangements of elements, additional intervening elements,devices, features, or components may be present in an embodiment of thedisclosure.

1. A method for operating a shape memory alloy actuated aerostructurecomprising a first face sheet and a second face sheet, the methodcomprising: determining at least one characteristic of a shape memoryalloy actuated aerostructure to be optimized; determining a flightcondition temperature based on current flight conditions; controlling ashape memory alloy temperature of at least one portion of at least oneshape memory alloy actuator to optimize the at least one characteristic,comprising controlling the shape memory alloy temperature of the leastone portion to select and maintain a shape of the at least one shapememory alloy according to the determined flight condition temperature,the at least one shape memory alloy actuator comprising a lattice ofshape memory alloy metal located between the first face sheet and thesecond face sheet, and coupled at substantially maxima of the at leastone shape memory alloy actuator to the first face sheet at two or morelocations on the first face sheet, and coupled at substantially minimaof the at least one shape memory alloy actuator to the second face sheetat two or more locations on the second face sheet, wherein the firstface sheet and the second face sheet are each made of materials thatdiffer from the shape memory alloy metal; and obtaining an optimum areafor a variable area fan nozzle by morphing the shape memory alloyactuated aerostructure thereby reducing noise.
 2. The method accordingto claim 1, wherein the at least one characteristic is optimized basedon at least one flight condition.
 3. The method according to claim 1,wherein the at least one characteristic comprises at least one memberselected from the group consisting of: aerodynamic noise, aerodynamicdrag, and aerodynamic lift.
 4. The method according to claim 1, whereinthe controlling step further comprises: monitoring the temperature ofthe at least one portion of the at least one shape memory alloyactuator; and providing a temperature change by heating or cooling ofthe at least one portion of the at least one shape memory alloyactuator.
 5. The method according to claim 1, wherein the controllingstep further comprises thermally controlling the at least one portion ofthe at least one shape memory alloy actuator to change an area of thevariable area fan nozzle by morphing the shape memory alloy actuatedaerostructure based on at least one flight condition.
 6. The methodaccording to claim 1, wherein the controlling step further comprisesadjusting at least one temperature for each of a plurality of sectionsof the at least one shape memory alloy actuator respectively.
 7. Themethod according to claim 1, wherein the controlling step furthercomprises: thermally controlling the at least one shape memory alloyactuated aerostructure to extend into a flow path of a gas flow emittedfrom the variable area fan nozzle for a first set of flight conditions;and thermally controlling the at least one shape memory alloy actuatedaerostructure to extend away from the flow path for a second set offlight conditions.
 8. The method according to claim 1, furthercomprising extending the at least one shape memory alloy actuatedaerostructure from a lip area of the variable area fan nozzle inproximity to a flow path of a gas flow emitted from the variable areafan nozzle.
 9. The method according to claim 8, further comprisingdeforming the at least one shape memory alloy actuated aerostructurebetween a first position in proximity to the flow path to a secondposition extending into the flow path.
 10. The method according to claim8, further comprising deforming the at least one shape memory alloyactuated aerostructure from a first position in proximity to the flowpath to a second position extending away from the flow path.
 11. Themethod according to claim 1, wherein: the lattice comprises a sinusoidalstrip of shape memory alloy metal; and the at least one location and thetwo or more locations are located at substantially maxima and minima ofthe sinusoidal strip respectively.
 12. The method according to claim 1,wherein controlling the shape memory alloy temperature of at least oneportion of at least one shape memory alloy actuator comprises heatingthe shape memory alloy actuator to a plurality of temperatures thatinclude the shape memory alloy temperature.
 13. A method for configuringa shape memory alloy actuated aerostructure comprising a first facesheet and a second face sheet, the method comprising: configuring atleast one shape memory alloy actuator comprising a lattice of shapememory alloy metal; locating the at least one shape memory alloyactuator between the first face sheet and the second face sheet, whereinthe first face sheet and the second face sheet are each made ofmaterials that differ from the shape memory alloy metal; coupling the atleast one shape memory alloy actuator at substantially maxima of the atleast one shape memory alloy actuator to the first face sheet at two ormore locations on the first face sheet; coupling the at least one shapememory alloy actuator at substantially minima of the at least one shapememory alloy actuator to the second face sheet at two or more locationson the second face sheet; and configuring the shape memory alloyactuated aerostructure to morph to obtain an optimum area for a variablearea fan nozzle thereby reducing noise generated by the variable areafan nozzle using a controller configured to control a shape memory alloytemperature of least one portion of the shape memory alloy actuatedaerostructure to select and maintain a shape of the shape memory alloyactuated aerostructure according to a determined flight conditiontemperature.
 14. The method according to claim 13, further comprisingconfiguring the at least one shape memory alloy actuated aerostructureto extend from a lip area of the variable area fan nozzle in proximityto a flow path of a gas flow emitted from the variable area fan nozzle.15. The method according to claim 14, further comprising: configuringthe at least one shape memory alloy actuated aerostructure to deformbetween a first position in proximity to the flow path to a secondposition extending into the flow path; and configuring the at least oneshape memory alloy actuated aerostructure to deform from the firstposition in proximity to the flow path to a third position extendingaway from the flow path.
 16. The method according to claim 13, furthercomprising: configuring the lattice to comprise a sinusoidal strip ofshape memory alloy metal; and locating the at least one location and thetwo or more locations at substantially maxima and minima of thesinusoidal strip respectively.
 17. The method according to claim 13,further comprising coupling the shape memory alloy actuatedaerostructure to at least one part of a thrust reverser sleeve.
 18. Themethod according to claim 13, further comprising coupling the shapememory alloy actuated aerostructure to at least one member selected fromthe group consisting of: a fan nozzle, and a core nozzle.
 19. The methodaccording to claim 13, further comprising configuring the shape memoryalloy actuated aerostructure to comprise at least one member selectedfrom the group consisting of: a variable area fan nozzle panel, and avariable geometry chevron.
 20. The method according to claim 13, whereinconfiguring the shape memory alloy actuated aerostructure comprisingheating the shape memory alloy actuator to a plurality of temperaturesthat include the shape memory alloy temperature.